The present invention generally relates to an oxabicyclo monomer and a photoresist polymer formed therefrom, a photoresist composition containing said polymer, and a method of forming a photoresist micro pattern using the polymer. During the manufacture of a micro circuit of a highly integrated semiconductor device, the polymer of the present invention can be used as a photoresist in a photoresist lithography process using a KrF(248 nm) or an ArF(193 nm) light source. These are the light sources usually applied in the manufacture of 1 G and 4 G Dynamic Random Access Memory ("DRAM") semiconductor devices.
In general, an ArF photoresist usually requires excellent etching resistance and adhesiveness as well as low light absorbance at 193 nm wavelength. The ArF photoresist should also be developable by using a 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution. Up to now, many researchers have focused on photoresist resins having an etching resistance and transparency to 193 nm wavelength similar to that of novolac-type resins. This work is described, for example, in the following articles: "Synthesis and Dissolution Characteristics of Novel Alicyclic Polymers With Monoacid Ester Structures" (Takashi Hattori et al., Journal of Photopolymer Science and Technology, 1997, Vol. 10, No. 4, pp. 535-544.), "New Protective Groups in Alicyclic Methacrylate Polymers for 193 nm Resists" (Ibid., pp. 545-550), and "Chemically Amplified Resist Based on High Etch-Resistant Polymers for 193 nm Lithography" (Ibid., pp. 561-570) and so on. To obtain an etching resistance similar to that of a novolac-type resin, an ArF photoresist resin should contain an alicyclic group. However, alicyclic-type resins generally have poor adhesiveness. A micro pattern using an alicyclic-type resin is illustrated in FIG. 1. The alicyclic-type resin used to form the pattern in FIG. 1 has good resolution, but poor adhesiveness. Thus, a pattern collapse occurs such as that shown in FIG. 1. As a result, it is very difficult to practically apply such a resist to a semiconductor device.
The photosensitive properties of the photoresist resin are affected by the monomer type used to form the photoresist resin. Thus, photosensitivity, etching resistance, adhesiveness, resolution, and so on varies depending on the monomer type introduced into the photoresist resin. In addition, the monomers conventionally used to form the photoresist resin are expensive, thus making it difficult to mass-produce the photoresist resin using conventional monomers. Therefore, the invention of a monomer which would allow the mass-production of a photoresist resin having excellent photosensitive properties, is advantageous.